Spiders in Manitoba

What spiders live in Manitoba?

Manitoba runs from tall-grass prairie and aspen parkland in the south, through the lake country of the Interlake, into boreal forest and finally tundra on the Hudson Bay coast. Spiders live right across that range — there are wolf spiders hunting on the beach ridges at Churchill — but the species people notice are concentrated in the settled south, around Winnipeg, Brandon, the Red River valley and the Whiteshell.

The short list profiled on this page is a snapshot of the province's most-photographed spiders rather than a complete inventory; the real fauna runs to hundreds of species, most of them small sheet-web weavers and Pardosa wolf spiders that go unnoticed underfoot. What people send in for identification is almost always a big late-summer orb web, a fishing spider at the cottage, or a dark spider in the basement.

Which Manitoba spiders are dangerous?

Only one, and it is uncommon. The western black widow reaches the north-eastern edge of its range in southern Manitoba, where it turns up in warm, dry, sandy country such as the Carberry sandhills and Spruce Woods, in rodent burrows, under debris and in the sheltered cavities of old buildings and machinery. The mature female is glossy black with a red hourglass beneath a bead-shaped abdomen. Her bite can cause cramping pain that spreads from the limb into the abdomen and back, with sweating, nausea and raised blood pressure. Older descriptions of "severe damage" overstate it: the syndrome is painful and worth a hospital visit, but it is treatable and deaths are almost unheard of.

The hobo spider was listed here among the most dangerous spiders in the province. Both halves of that claim are shaky. The necrotic-bite reputation collapsed when researchers could not reproduce it, and the US Centers for Disease Control removed the species from its list of spiders of concern in 2017. It is also far from a Manitoba staple — this introduced European funnel weaver is firmly established in British Columbia and the Pacific Northwest, with only scattered records inland, and it cannot be identified from a photograph even by an arachnologist.

There are no recluse spiders in Manitoba. Loxosceles is not established anywhere in Canada, so a brown recluse bite diagnosed in Winnipeg is far more likely to be a bacterial skin infection or another skin condition. The dark, glossy spiders found in Manitoba basements are usually cobweb spiders such as the false black widow and its relatives, which lack the hourglass and are harmless.

Where you meet them

Lakes, rivers and cottage country

Manitoba's giants are the striped fishing spider and the dark fishing spider, both members of the nursery web spider family. The striped fishing spider stays close to water, resting on rocks and dock timbers with its front legs on the surface film to feel for vibrations, and it can run across open water or dive under it to escape. The dark fishing spider ranges further from shore, climbing tree trunks and walls, and is the one most likely to appear inside a lakeside cabin. Both are shy, and neither is medically significant.

Gardens, fences and porches

The cross orb weaver, a European species now naturalised across southern Canada, is the classic Manitoba garden spider: a stout, pale-to-rust animal with a cross of white dashes on the abdomen, sitting head-down in a wheel web slung between a fence rail and a shrub. Native orb weavers such as the marbled and shamrock species join it in hedgerows and at woodland edges.

Prairie, dunes and open ground

Bare, sun-warmed ground belongs to the wolf spiders, which carry their egg sacs attached to the spinnerets and then their spiderlings on their backs. Sweep a headlamp across a sandy path at night and their eyeshine answers back. The same warm, sandy habitat is where the province's few widows live, which is a good reason to wear gloves when moving boards and debris in the far south.

Spider season in Manitoba

The province's short, hot summer compresses everything. Spiderlings hatch or emerge in late spring, feed hard through July, and reach adult size in August and early September — which is why webs seem to appear all at once and why mature males start turning up indoors. Insect abundance drives the whole cycle, so a warm, wet summer produces a conspicuous spider autumn.

Manitoba winters are severe, and spiders handle them by shutting down rather than moving. Most overwinter as eggs in a silk sac, or as part-grown juveniles tucked into leaf litter, grass tussocks and bark crevices, where a stable snowpack insulates them far better than open cold; their tissues accumulate compounds that prevent ice crystals forming. The full range of strategies is described in our guide to where spiders go in the winter.

Common mix-ups

The one that matters is widow versus false widow. Both are dark, glossy and round-bodied, but only a mature female widow carries a red hourglass on the underside of the abdomen; Steatoda species show at most a pale crescent at the front, and they are much more widely distributed in the province than true widows.

The second is fishing spider versus wolf spider. Both are large, brown and hairy, but a fishing spider has a longer, flatter body, banded legs and sits still at the water's edge, while a wolf spider is bulkier-eyed and runs. And every September a wave of harvestmen and crane flies is reported as spiders; harvestmen have one body section, no silk glands and no venom at all.

Common Spiders in Manitoba

• Sand Bear Wolf Spider
• Cross Orb-weaver Spider

Large Spiders in Manitoba

• Striped Fishing Spider
• Dark Fishing Spider

Most Dangerous Spiders in Manitoba

• Western Black Widow Spider
• Hobo Spider

Most Venomous Spiders in Manitoba

Comb-footed Spiders

Cobweb SpidersWestern Black Widow (Latrodectus hesperus)Identify the western black widow (Latrodectus hesperus): the red hourglass, the male and spiderling patterns, its web, range and how serious

Funnel Weaver Spiders

Funnel Weaver SpidersHobo (Eratigena agrestis)Identify the hobo spider (Eratigena agrestis): size, chevron abdomen, funnel web, where it lives, and why its bite is not considered necroti

Less Venomous Spiders in Manitoba

Nursery Web Spiders

Nursery Web SpidersStriped Fishing (Dolomedes scriptus)Identify the striped fishing spider (Dolomedes scriptus): size, pale side stripes, stream-bank habitat, how it hunts on water and whether itNursery Web SpidersDark Fishing (Dolomedes tenebrosus)Identify the dark fishing spider (Dolomedes tenebrosus): size, chevron markings, where it lives in North America, and whether its bite is da

Orb-weaver Spiders

Orb WeaversCross Orb Weaver (Araneus diadematus)Identify the cross orb weaver (Araneus diadematus) by the white cross on its abdomen: size, colour, web, egg sac, range and whether the bite

Living with Manitoba's spiders

Very little needs doing, and almost none of it involves chemicals:

• Wear gloves when moving boards, rocks or stored equipment in the sandy far south, the only widow habitat in the province.
• Shake out boots and gloves stored in a garage, shed or cottage crawlspace.
• Seal gaps under doors and around basement windows in August, when wandering males come indoors.
• Vacuum webs rather than spraying; removing the web and the insects that feed it works better than insecticide.
• Leave garden orb weavers in place until the frost takes them, since each web removes hundreds of mosquitoes and flies.

The fauna here is essentially the same as in Saskatchewan, and shades eastwards into the richer, more forested list of Ontario.